Let's do some math ..  Rounding examples of 7 random hypothetical purchases:
Case	Tag   Price	Sales   Tax %	Raw Total   Incl. Sales Tax	Rounded   to Penny	Rounded   to Nickel	Rounded   to Dime
Purchase #1	$176.46	11.595%	$196.9205	$196.92	$196.90	$196.90
Purchase #2	$202.59	10.573%	$224.0098	$224.01	$224.00	$224.00
Purchase #3	$89.34	11.869%	$99.9438	$99.94	$99.95	$99.90
Purchase #4	$230.43	13.741%	$262.0934	$262.09	$262.10	$262.10
Purchase #5	$190.78	4.187%	$198.768	$198.77	$198.75	$198.80
Purchase #6	$82.33	11.304%	$91.6366	$91.64	$91.65	$91.60
Purchase #7	$221.27	6.695%	$236.084	$236.08	$236.10	$236.10
7 purchase totals =	$1,193.20		$1,309.4561	$1,309.45	$1,309.45	$1,309.40